KR20150050511A - A method of manufacturing separator for electrochemical device and separator for electrochemical device manufactured thereby - Google Patents

Abstract

A manufacturing method of a separation film for an electrochemical device according to an embodiment of the present invention comprises; a step of excluding a resin composition containing polyolefin and a plasticizer; a step of obtaining a polyolefin film by elongating the resin composition; a step of obtaining a porous polyolefin film by extracting the plasticizer from the plasticizer film; a step of coating slurry for the formation of a porous coating layer on at least one side of the porous polyolefin film; and a step of obtaining a complex separating film wherein the porous coating layer is formed by thermal-fixating the porous polyolefin film wherein the slurry is coated. According to an embodiment of the present invention, processes of thermal fixation/winding and slitting/unwinding executed between a plasticizer extracting process and a slurry coating process can be omitted dramatically by manufacturing a separating film in the order of an extruding process, an elongation process, the plasticizer extracting process, the slurry coating process, and a thermal fixation process.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator for electrochemical devices and a separator for electrochemical devices manufactured therefrom,

The present invention relates to a process for producing a separator for electrochemical devices and a separator for electrochemical devices manufactured therefrom, and more particularly to a process for producing a separator for electrochemical devices having improved mechanical / thermal performance and a process for producing And a separation membrane for chemical devices.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified.

Electrochemical devices have attracted the greatest attention in this respect, among which the development of rechargeable secondary batteries has become a focus of attention. In recent years, in order to improve the capacity density and specific energy in developing such batteries, And research and development on the design of the battery.

It is very important to evaluate and secure safety in such an electrochemical device. The most important consideration is that the electrochemical device should not injure the user in case of malfunction. For this purpose, the safety standard strictly regulates the ignition and fuming in the electrochemical device. In the safety characteristics of the electrochemical device, there is a high possibility that the electrochemical device will be overheated to cause thermal runaway or explosion if the separator is penetrated. Particularly, a polyolefin porous substrate, which is typically used as a separator of an electrochemical device, exhibits extreme heat shrinkage behavior at a temperature of 150 DEG C or more due to characteristics of the manufacturing process including material properties and elongation, There is a problem.

In order to solve this problem, a composite membrane including a porous coating layer having a porous substrate coated with a slurry containing inorganic particles or organic particles and a binder polymer on at least one surface of a polyolefin porous substrate having a plurality of pores has been proposed. In such a composite separator, the inorganic / organic particles in the coating layer coated on the polyolefin porous substrate serve as a support for maintaining the physical form of the coating layer, thereby suppressing the heat shrinkage of the polyolefin porous substrate when the lithium ion battery is overheated.

1, the conventional process for producing such a separation membrane comprises a step of extruding a polyolefin resin composition, a step of stretching an extruded resin composition to obtain a sheet-like film, a step of extracting a plasticizer from the obtained separation membrane, A step of heat-setting the porous film, a step of first winding / slitting the heat-set porous film, a step of unwinding, a step of applying the coating slurry, a step of drying the coating slurry, a step of winding the secondary winding / A step of slitting and a step of packaging the product.

According to this conventional process, the heat setting process is limited to a temperature at which the polyolefin film is not melted. Further, after the slurry is coated on the porous substrate and dried, there is a problem that it is difficult to perform the additional heat fixation process because structural stability may be destroyed.

On the other hand, Japanese Patent No. 5543715 discloses a process for producing a polyolefin resin by the steps of (i) melt kneading and extruding a polyolefin resin, a plasticizer or a polyolefin resin, a plasticizer and an inorganic agent, (ii) a step of stretching the obtained extrudate, (iii) A separator for a nonaqueous electrolyte battery including a step of extracting an inorganic agent. However, since this is not a method of coating a slurry of inorganic particles or the like after forming the porous substrate, the order of the slurry coating and the heat fixing step and the specific conditions thereof are not mentioned.

Korean Patent No. 10-0406690 discloses a multi-component film used as a separator for an electrochemical device, comprising: i) providing a polymer support layer film; Ii) dissolving the gelled polymer in a solvent to prepare a gelled polymer solution; Iii) forming a gelated polymer layer on one side or both sides of the support layer film of step i) from the gelled polymer solution of step ii) to produce a multilayered film; And iv) stretching the multilayer film of step iii) and thermally fixing the multilayer film. However, this document does not disclose a step of forming a porous polymer layer by forming a gelled polymer layer on a porous substrate, and forming a porous coating layer by coating a slurry containing organic particles or inorganic particles. Further, in this document, in the case of a composite film having a porous coating layer comprising organic particles and / or inorganic particles, the resulting multilayered film is first stretched and fixed after coating the polymeric support layer film on the gelated polymer layer, There is a problem that cracks are generated in the coating layer in the TD direction when stretching, which is a limitation in application.

Japanese Patent No. 5543715 (Apr. 9, 2014) Korean Patent No. 10-0406690 (November 21, 2003)

DISCLOSURE Technical Problem The present invention has been made in view of the above problems, and it is an object of the present invention to provide a composite membrane in which a porous coating layer is structurally stabilized, a process cost is reduced, And to provide a method for producing a separation membrane for a device.

It is to be understood, however, that the technical scope of the present invention is not limited to the above-mentioned problems, and other technical subjects not mentioned above can be understood by those skilled in the art from the description of the invention described below.

According to an aspect of the present invention,

Extruding a resin composition containing a polyolefin and a plasticizer; Stretching the extruded resin composition to obtain a polyolefin film; Extracting the plasticizer from the obtained polyolefin film to obtain a porous polyolefin film; Coating at least one surface of the porous polyolefin film with a slurry for forming a porous coating layer; And a step of thermally fixing the porous polyolefin film coated with the slurry to obtain a composite separator having a porous coating layer formed thereon.

Wherein the extruded resin composition is subjected to uniaxial stretching at least once in the MD direction or TD direction or by biaxial stretching at least once in the MD and TD directions.

The temperature of the open and defined temperature is not more than Tm - 1 DEG C, and Tm may be the melting point of the polyolefin.

The open and defined temperature may be 131 ° C to 134 ° C.

The heat setting may be performed using a heat source oriented in a direction perpendicular to the surface of the slurry coated on the porous polyolefin film.

Wherein the polyolefin is selected from the group consisting of polyethylene; Polypropylene; Polybutylene; Polypentene: polyhexene: polyolefin: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, and octene, or a mixture thereof.

Examples of the plasticizer include paraffin oil, mineral oil, wax, soybean oil, phthalic acid esters, aromatic ethers, fatty acids having 10 to 20 carbon atoms; Fatty acid alcohols having 10 to 20 carbon atoms; And fatty acid esters.

The porous polyolefin film may have a thickness of 5 to 50 탆, a pore size and a porosity of 0.01 to 50 탆 and 10 to 95%, respectively.

The slurry for forming a porous coating layer may include at least one of inorganic particles and organic particles, a binder polymer, and a solvent.

The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, Polybutylene terephthalate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyethylene) oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylpolyvinylalcohol, No ethylcellulose But are not limited to, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, Or a mixture thereof.

The inorganic particles may be inorganic particles having a dielectric constant of 5 or more, lithium ion transferring ability, or a mixture thereof.

The inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) ₃ O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO _2, SiC Or a mixture thereof.

Wherein the inorganic particles having lithium ion transferring ability are lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass (0 < 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , x <4, 0 <y < 1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 based glass ( _{Li x Si y S z, 0} <x <3, 0 <y <2, 0 <z <4), P 2 S 5 based _{glass (Li x P y S z} , 0 <x <3, 0 <y < 3, 0 < z < 7), or a mixture thereof.

Wherein the organic particles are selected from the group consisting of polystyrene, polyethylene, melamine resin, phenol resin, cellulose, cellulose modified product, polypropylene, polyester, polyphenylene sulfide, polyaramid, polyamideimide, polyimide, butyl acrylate, &Lt; / RTI &gt; or mixtures thereof.

The average particle diameters of the inorganic particles and the organic particles may independently be 0.001 to 10 탆.

And winding and slitting the composite separator.

The step of coating the slurry for forming a porous coating layer may not include the step of heat setting and the step of winding and slitting.

The method may further include packaging the composite separator having completed the winding and slitting.

According to an aspect of the present invention, there is provided a separation membrane for an electrochemical device produced by the above-described production method.

According to an aspect of the present invention, there is provided an electrochemical device including a cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the separator for the electrochemical device.

The electrochemical device may be a lithium secondary battery.

According to one embodiment of the present invention, the separation membrane is manufactured in the order of the extrusion process, the drawing process, the plasticizer extraction process, the slurry coating process, and the heat setting process, / The process of winding and slitting / unwinding can be skipped drastically.

In addition, according to one embodiment of the present invention, it is possible to improve the physical properties of the composite separator, reduce the production cost, improve the quality, improve the production yield, realize the ultra wide coating, You can have an advantage.

In particular, according to one embodiment of the present invention, since the slurry coating is performed on the porous polyolefin film, thermal fixation is performed at a higher temperature than the conventional heat fixing temperature, thereby improving the mechanical and thermal performance, A separator can be provided and the length of the heat-fixing oven can be compactly reduced, thereby enabling space utilization, process cost and production cost reduction.

In addition, according to one embodiment of the present invention, since the heat fixing step is omitted before the slurry coating step, space utilization and cost reduction can be achieved by simultaneously using the heat-fixing oven and the drying oven separately.

Further, since the heat applied in the heat fixing process is transferred to the polyolefin film through the porous coating layer, the composite membrane having the porous coating layer formed by performing the slurry coating followed by the heat setting can be thermally fixed at a relatively high temperature, The wettability of the coating slurry to the fibril structure is improved.

Also, since the heat applied in the heat fixing process is transferred to the polyolefin film through the porous coating layer, the polyolefin film has a thinner diameter fibril, thereby increasing the fibril number density per unit area and forming a porous coating layer The surface area of the interface between the coating slurry and the coating slurry is increased. This makes it easier to maintain the physical form of the polyolefin film, thereby improving the heat shrinkage ratio of the composite separator and improving the peel strength of the coating layer.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention. And should not be construed as limiting.
1 is a conceptual view showing a conventional process for producing a separator for electrochemical devices.
FIG. 2 is a conceptual view showing a method of manufacturing a separation membrane for an electrochemical device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor should appropriately define the concept of terms in order to describe his invention in the best way. It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

According to an aspect of the present invention, there is provided a method of manufacturing a separation membrane for an electrochemical device, comprising: extruding a resin composition containing a polyolefin and a plasticizer; Stretching the extruded resin composition to obtain a polyolefin film; Extracting the plasticizer from the obtained polyolefin film to obtain a porous polyolefin film; Coating at least one surface of the porous polyolefin film with a slurry for forming a porous coating layer; And a step of heat-setting the porous polyolefin film coated with the slurry to obtain a composite separator having a porous coating layer formed thereon.

FIG. 2 is a conceptual diagram illustrating a method for fabricating a separation membrane for an electrochemical device according to an embodiment of the present invention.

Referring to FIG. 2, the method for fabricating a separation membrane for an electrochemical device according to an embodiment of the present invention may further include winding and slitting a composite membrane that has been heat-set to obtain a final product. The method may further include packaging the composite separator having completed the winding and slitting.

In addition, the method of manufacturing the separation membrane for an electrochemical device according to an embodiment of the present invention is characterized in that, compared with the conventional manufacturing method shown in FIG. 1, But does not include a step of slitting.

Specifically, according to one embodiment of the present invention, a separation membrane is manufactured in the order of an extrusion process, a drawing process, a plasticizer extraction process, a slurry coating process, and a heat fixing process, After the extraction process, the heat fixing process, the winding and slitting process, and the unwinding process are not required, and these processes can be skipped drastically.

Hereinafter, each step will be described in detail.

First, in the extruding step, the polyolefin is not particularly limited as long as it is commonly used in the art. Specific examples of such polyolefins include polyethylene such as high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra high molecular weight polyethylene (UHMWPE) and the like; Polypropylene; Polybutylene; Polypentene: polyhexene: polyoctene: at least one copolymer of ethylene, propylene, butene, pentene, 4-methylpentene, hexene, and octene, or a mixture thereof, but is not limited thereto.

The plasticizer is not particularly limited as long as it is commonly used in the art. Non-limiting examples of such plasticizers include phthalic acid esters such as dibutyl phthalate, dihexyl phthalate, and dioctyl phthalate; Aromatic ethers such as diphenyl ether and benzyl ether; Fatty acids of 10 to 20 carbon atoms such as palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid; Fatty acid alcohols having 10 to 20 carbon atoms such as palmitic alcohol, stearic alcohol, and oleic alcohol; Mono-, di-, or triesters of palmitic acid, mono-, di-, or triesters of stearic acid. One in which a double bond of a saturated or unsaturated fatty acid or an unsaturated fatty acid having 4 to 26 carbon atoms in a fatty acid group such as oleic acid mono-, di-, or triester, mono -, di-, or triester of linoleic acid is substituted with an epoxy Or a fatty acid ester in which two or more fatty acids are ester-bonded with an alcohol having 1 to 8 hydroxyl groups and 1 to 10 carbon atoms.

The plasticizer may be a mixture containing two or more of the above-mentioned components.

The weight ratio of the polyolefin to the plasticizer may be 80:20 to 10:90, preferably 70:30 to 20:80, and preferably 50:50 to 30:70. If the weight ratio of polyolefin is larger than 80:20, the porosity decreases and the pore size decreases. Since the interconnection between the pores is small and the permeability is greatly decreased, the viscosity of the polyolefin solution increases, If the weight ratio is less than 10:90 and the content of the polyolefin is decreased, the kneading property between the polyolefin and the plasticizer is lowered, so that the polyolefin is extruded into a gel form without thermodynamically kneading the plasticizer into the plasticizer, Uniformity, and the like, and the strength of the produced separation membrane may be lowered.

In order to produce the composite membrane in the present invention, first, a part or the whole of the material is mixed using a Henschel mixer, a ribbon blender, a tumbler blender, or the like. Then, it is melted and kneaded by a screw extruder such as a single screw extruder, a twin screw extruder, a kneader or a mixer, and extruded from a T-die or a ring-shaped die. The kneaded / extruded melt can be solidified by compression cooling. Examples of the cooling method include direct contact with a cooling medium such as cold wind or cooling water, contact with a roll or a press cooled with a coolant, and the like.

Subsequently, the extruded resin composition is stretched to obtain a polyolefin film. The stretching method may be carried out by a conventional method known in the art, and examples thereof include MD (longitudinal) uniaxial stretching by a roll stretcher, TD (transverse direction) uniaxial stretching by a tenter, roll stretcher and tenter, Or simultaneous biaxial stretching by combination of tenter and tenter, simultaneous biaxial stretching by simultaneous biaxial tenter or inflation molding, and the like. Specifically, the extruded resin composition may be subjected to uniaxial stretching at least once in the MD or TD direction, or by biaxial stretching at least once in the MD and TD directions.

The stretching ratio may be 3 times or more, preferably 5 to 10 times in the longitudinal direction and 20 times or more in the transverse direction, and 20 times or more, preferably 20 to 80 times in the total stretching ratio (total surface multiplication factor).

If the stretching ratio in one direction is less than 3 times, the orientation in one direction is not sufficient and the physical property balance between the longitudinal direction and the transverse direction is broken, and the tensile strength and puncture strength may be lowered. If the total stretching ratio is less than (20) times, unstretching may occur and pore formation may not be performed. If the total stretching ratio is more than (80) times, breakage may occur during stretching and the shrinkage percentage of the final film may increase have.

In this case, the stretching temperature may be varied depending on the melting point of the polyolefin used and the concentration and type of the plasticizer, and preferably, the stretching temperature is selected in a range of temperatures in which 30 to 80% by weight of the crystalline portion of the polyolefin in the film is melted It is appropriate.

If the stretching temperature is selected in a temperature range lower than the temperature at which 30% by weight of the crystalline portion of the polyolefin in the sheet molding is melted, the softness of the film is poor and the stretchability is deteriorated, Occurs. On the other hand, if the stretching temperature is selected in a temperature range higher than the melting temperature of 80% by weight of the crystalline portion, stretching is easy and unstretched occurrence is small, but thickness deviation occurs due to partial over-stretching, . On the other hand, the degree of melting of the crystal part with temperature can be obtained from DSC (differential scanning calorimeter) analysis of the film molding.

Then, the plasticizer is extracted from the stretched film to obtain a porous polyolefin film. Specifically, in the stretched film, the plasticizer is extracted using an organic solvent and dried.

The extraction solvent used for the extraction of the plasticizer is preferably a poor solvent for polyolefin, a good solvent for the plasticizer, and a boiling point lower than the melting point of the polyolefin, so that drying is preferable. Nonlimiting examples of such an extraction solvent include hydrocarbons such as n-hexane and cyclohexane, halogenated hydrocarbons such as methylene chloride, 1,1,1-trichloroethane, and fluorocarbon, alcohols such as ethanol and isopropanol, And ketones such as acetone and 2-butanone.

As the extraction method, any general solvent extraction method such as an immersion method, a solvent spray method, an ultrasonic method or the like can be used individually or in combination. The content of the residual plasticizer in the extraction should preferably be not more than 1% by weight. When the amount of the residual plasticizer exceeds 1% by weight, the physical properties are lowered and the permeability of the porous film is decreased. The amount of the residual plasticizer may be influenced by the extraction temperature and the extraction time. The extraction temperature is preferably high to increase the solubility of the plasticizer and the organic solvent. However, considering safety problems due to the boiling of the organic solvent, . If the extraction temperature is lower than the solidifying point of the plasticizer, the extraction efficiency is greatly lowered, and therefore, it must be higher than the solidifying point of the plasticizer.

Further, the extraction time depends on the thickness of the porous polyolefin film to be produced, but in the case of 10 to 30 탆 thickness, 2 to 4 minutes are suitable.

The thickness of the porous polyolefin film obtained above is not particularly limited, but is preferably in the range of 5 to 50 占 퐉, and the pore size and porosity present in the porous substrate are also not particularly limited, but 0.001 to 50 占 퐉 and 10 to 99% desirable.

Then, at least one surface of the porous polyolefin film is coated with a slurry for forming a porous coating layer. For this purpose, a slurry for forming a porous coating layer must first be prepared. The slurry is prepared by dispersing a binder polymer together with at least one of inorganic particles and organic particles in a solvent. That is, the slurry may contain the inorganic particles alone, the organic particles alone, or the inorganic particles and the organic particles at the same time.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance. When inorganic particles having a high dielectric constant are used as the inorganic particles, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte is also increased, and ion conductivity of the electrolyte can be improved.

Non-limiting examples of the inorganic particles include high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having lithium ion-transporting ability, or a mixture thereof.

Non-limiting examples of inorganic particles greater than a dielectric constant of 5 is _{BaTiO 3, Pb (Zr, Ti} ) O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB (Mg 3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO _2, SiC Or mixtures thereof.

The term "inorganic particle having lithium ion-transferring ability" as used herein refers to an inorganic particle containing a lithium element but not having lithium stored therein and having a function of moving lithium ions. The inorganic particle has a lithium ion- examples include lithium phosphate (Li ₃ PO _4), lithium titanium phosphate _{(Li x Ti y (PO 4} ) 3, 0 <x <2, 0 <y <3), lithium aluminum titanium phosphate (Li _x Al _y Ti _z (LiAlTiP) _x O _y series such as (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), Li _3.25 Ge _0.25 P _0.75 S (0 <x <4, 0 <y <13) ₄ lithium such as germanium Mani help thiophosphate lithium such as _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), Li 3 N SiS ₂ series glass (Li _x Si _y S _z , 0 < x < ₂₎ such as nitride (Li _x N _y , 0 <x <4, 0 <y <2), Li ₃ PO ₄ -Li ₂ S- 3, 0 <y <2, 0 <z <4), LiI -Li has a P ₂ S ₅ based _{glass (Li x P y S z} , 0 <x <3, 0 <y <3, 0 <z <7) or a mixture thereof, such as ₂ SP ₂ S _5.

The organic particles contained in the slurry are advantageous in terms of air permeability, heat shrinkability and peel strength, and are excellent in binding property with the binder polymer.

Nonlimiting examples of organic particles that can be used in the slurry for forming the porous coating layer include polystyrene, polyethylene, melamine resin, phenol resin, cellulose, modified cellulose (such as carboxymethylcellulose), polypropylene, A copolymer of butyl acrylate and ethyl methacrylate (for example, a copolymer of butyl acrylate and ethyl methacrylate), a polyalkylene sulfide, a polyamide, a polyamideimide, a polyimide, a copolymer of butyl acrylate and ethyl methacrylate Crosslinked polymers, etc.), and the like. The organic particles may be composed of two or more kinds of polymers.

The size of the inorganic particles or organic particles is not limited, but may be in the range of 0.001 to 10 탆 in terms of forming a coating layer having a uniform thickness and having an appropriate porosity.

The binder polymer used in the slurry for forming the porous coating layer is not particularly limited as long as it can function as a link between inorganic particles or organic particles and stably fix them. Non-limiting examples of the binder polymer include polyvinylidene fluoride-hexafluoro Polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose but are not limited to, acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, Pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide. These resins may be used alone or in combination of two or more thereof. Two or more species may be used in combination.

The composition ratio of the particles in the slurry and the binder polymer for forming the porous coating layer may be, for example, in the range of 50:50 to 99: 1 by weight or 70:30 to 95: 5. If the content of the particles relative to the binder polymer is too small, improvement of the thermal stability of the separation membrane may be deteriorated, voids formed between the particles may not be formed sufficiently, pore size and porosity may be decreased, have. On the other hand, if the particles are contained in an excessively large amount relative to the binder polymer, the peeling resistance of the porous coating layer may be weakened.

As the solvent contained in the slurry, it is preferable that the dispersion of the particles and the binder polymer can be made uniform, and can be easily removed thereafter. Non-limiting examples of usable solvents include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone ( N-methyl-2-pyrrolidone, NMP), cyclohexane, water or mixtures thereof.

The slurry for forming a porous coating layer is coated on at least one surface of the porous polyolefin film. The specific coating method may be a conventional coating method known in the art. For example, a dip coating, a die coating, A roll coating, a comma coating, a mixing method thereof, or the like. Further, the porous coating layer can be selectively formed on both or only one side of the porous polyolefin film.

Then, the porous polyolefin film coated with the slurry is heat-set to obtain a composite separator having a porous coating layer.

The hot fix is a process of fixing the film and applying heat to forcefully hold the film to be shrunk to remove residual stress. If the heat fixing temperature is higher, the shrinkage rate is decreased. However, if the heat setting temperature is too high, the polyolefin film is partially melted, so that the formed micropores may be clogged and the permeability may be lowered.

In the present invention, since the plasticizer is extracted after the polyolefin film is stretched, and then the slurry for forming the porous coating layer is coated and heat-set is performed, unlike the process of extracting the plasticizer after stretching with the polyolefin film and heat- Since the coated slurry, not the polyolefin film, is thermally stable, the polyolefin film is not directly heated.

Therefore, melting of the polyolefin film can be suppressed even when heat setting is performed at a higher temperature than the conventional method. Further, since the amount of heat directly applied to the polyolefin film is small, the fibril thickness of the polyethylene-based adjacent to the porous coating layer is formed thinner than that of the conventional fibrillated polyolefin film. Accordingly, the fibrilar number density per unit area of the porous film surface adjacent to the porous coating layer is increased, so that the interface contact area with the coating slurry is increased and the glass transition temperature (T _g ) or melting point (T _m) than may be the wetting of the slurry to the fibrous structure of the porous polyolefin film improved when heat-treated at a high temperature region.

The temperature of the open and the defined temperature is preferably adjusted to Tm - 1 DEG C or less, where Tm corresponds to the melting point of the polyolefin.

According to one embodiment of the present invention, when polyethylene is used as the polyolefin, the open and defined temperature can be carried out at a temperature of from 131 to 135 DEG C, preferably from (131) to (133) DEG C, , The bonding strength (peel strength) between the porous coating layer and the porous polyolefin film is improved, and the structural stability can be secured and the thermal mechanical properties can be improved.

The heat setting may be performed using a heat source oriented in a direction perpendicular to the surface of the slurry coated on the porous polyolefin film.

Thus, since the hot heat source is directed in a direction perpendicular to the surface of the slurry coated on the porous polyolefin film, the probability that the binder polymer in the coated slurry is biased perpendicularly to the surface of the porous polyolefin film is rearranged Thereby forming a coating layer structure in which lithium ion migration is easy within the porous coating layer, and lithium ions can communicate with the pores formed in the porous polyolefin film. Also, the binder polymer between the particles and the binder polymer which is not completely bonded to the particles can be rearranged due to the recrystallization action by the high temperature heat source, and the resistance by the binder polymer can be greatly reduced. Such a tendency that the binder polymer is arranged in the vertical direction is particularly effective in the case of a binder polymer which is not well dispersed in a solvent such as cyanoethylpolyvinyl alcohol and forms a dense film on the porous polyolefin film to be.

The thickness of the porous coating layer may be in the range of 0.01 to 20 占 퐉, and the pore size and porosity may be in the range of 0.001 to 10 占 퐉, and the porosity may be in the range of 10 to 99% Lt; / RTI &gt; The pore size and porosity are mainly dependent on the size of particles used. For example, when particles having a particle size of 1 μm or less are used, the pores formed are also about 1 μm or less.

In the porous coating layer, the particles are charged and bound to each other by the binder polymer in a state of being in contact with each other, thereby forming an interstitial volume between the particles, and an interstitial volume The interstitial volume forms an empty space to form pores.

That is, the binder polymer adheres them to each other so that the particles can remain bonded to each other, for example, the binder polymer bonds and fixes the particles. In addition, the pores of the porous coating layer are pores formed by interstitial volumes between particles, which are voids, and are formed in particles that are substantially interfaced with each other in a closed packed or densely packed state . Such a pore structure is filled with an electrolyte solution to be injected at a later time, and the filled electrolyte can provide a path through which lithium ions, which are essential for operating the battery through the pores of the porous coating layer, are moved.

As described above, unlike the conventional manufacturing method shown in FIG. 1, the method of manufacturing a separation membrane according to an embodiment of the present invention includes a heat fixing step, a winding and slitting step, and an unwinding step after the plasticizer- It is not necessary.

Herein, the winding process refers to a step of winding the composite separator obtained after slurry coating and heat setting on the porous polyolefin film obtained through the extrusion / drawing / extraction steps onto a roller, and the slitting process is a process in which the composite separator And the unnecessary portions of both ends are cut at the time of winding of the wire. In the conventional method, it is necessary to wind the porous polyolefin film after the heat-setting and the slitting process, and then to unwind the film again to unwind the film to be slurry-coated. After the slurry coating and drying process, After the process, it finally reached the packaging stage.

At this time, according to one embodiment of the present invention, by reducing the winding and the slitting process from the conventional two to one, it is possible to prevent the loss of a part of the porous polyolefin film according to the winding and the slitting process, have.

In addition, since the unwinding step is omitted after the winding and slitting steps before the slurry coating step, space utilization and process cost can be reduced. In addition, since the slitting process before the slurry coating step or the winding / unwinding process is not performed, it is possible to perform a large-area coating with a large width, and the occurrence of defects such as wrinkles, pinholes and scratches between the final separators can be greatly reduced, The area also decreases. ,

Further, in place of the two separate heat treatment steps of the heat fixation step after the conventional plasticizer extraction and the drying step after the slurry coating, it is improved to a single heat treatment step of the heat fixation step after slurry coating, Without using an oven, only one heat-stable oven can be used, allowing space utilization and cost savings.

According to an aspect of the present invention, there is provided an electrochemical device including a cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the separator for the electrochemical device.

Such an electrochemical device may be manufactured according to a conventional method known in the art, and may be manufactured, for example, by injecting an electrolytic solution after assembling the cathode and the anode with the separator interposed therebetween have.

The electrode to be used together with the separator is not particularly limited and may be manufactured in a manner that an electrode active material is bound to an electrode current collector according to a conventional method known in the art.

Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof It is preferable to use a lithium composite oxide. As a non-limiting example of the anode active material, a conventional anode active material that can be used for an anode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium-adsorbing materials such as graphite or other carbon-based materials and the like are preferable.

Non-limiting examples of the cathode current collector include aluminum, nickel, or a combination thereof, and examples of the anode current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolyte solution that can be used in one embodiment of the present invention is a salt having a structure such as A ⁺ B ^- , where A ⁺ includes ions consisting of alkali metal cations such as Li ⁺ , Na ⁺ , K ^{+ -} it is _{^{PF 6 -, BF 4 -,}} Cl -, Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF ₂ SO _{2) 3} ^- anion, or a salt containing an ion composed of a combination of propylene carbonate (PC) such as, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl (DMP), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone Or an organic solvent composed of a mixture thereof, but the present invention is not limited thereto.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

As a process for applying the separator according to an embodiment of the present invention to a battery, a lamination, stacking and folding process of a separator and an electrode can be performed in addition to a general winding process.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the above-described embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Example 1

High-density polyethylene having a weight average molecular weight of 500,000 as a polyolefin and liquid paraffin having a kinematic viscosity of 68.00 cSt as a plasticizer were extruded at a temperature of 210 DEG C at a weight ratio of 35:65. The stretching temperature was set to 115 캜, and the stretching ratio was elongated seven times in the longitudinal direction. Subsequently, liquid paraffin as a plasticizer was extracted at a rate of 2 M / min using methylene chloride as an extraction solvent to obtain a porous polyolefin film having an average pore size of 0.04 탆.

Subsequently, Al ₂ O ₃ particles / cyanoethyl polyvinyl alcohol (Cyano resin CR-V, Shin-Etsu Chemical, Ltd.) / PVDF-HFP (LBG 2, Arkema , Inc.) / acetone were mixed so as to have a weight ratio of 13.5 / 0.225 / 1.275 / 85.

The slurry was coated on one side of the porous polyolefin film to a plasticizer extraction process in a thickness of 3.5 占 퐉, and then heat-set at 132.5 占 폚 at 5 m / min to prepare a 14.5 占 퐉 thick separation membrane having a porous coating layer. The porous coating layer of the obtained separation membrane had an average pore size of 0.4 mu m and an average porosity of 55%.

Example 2

As the slurry for forming a porous layer (product of PX9022, manufactured by Zeon), organic particles composed of a crosslinked polymer compound of butyl acrylate and ethyl methacrylate having an average particle diameter of 0.5 mu m, a binder (polybutyl acrylate), a dispersing agent (carboxymethylcellulose ) And ultrapure water as a solvent were prepared at a weight ratio of 18 / 1.5 / 0.5 / 80, and coating was carried out on both sides of the porous polyethylene film at a coating thickness of 4.0 탆. A separator for electrochemical devices was prepared in the same manner as in Example 1. The porous coating layer of the obtained separation membrane had an average pore size of 0.5 mu m and an average porosity of 61%.

Comparative Example 1

The same polyolefin film as used in Example 1 was heat set at 130 DEG C, and then a slurry for forming the same porous coating layer as used in Example 1 was coated on one side to a thickness of 3.5 mu m, To prepare a separator for an electrochemical device.

Comparative Example 2

The same porous polyolefin film as that used in Example 2 was heat-set at 130 캜, and on both sides thereof, a slurry for forming a porous coating layer as used in Example 2 was coated to a thickness of 4.0 탆, 5M / min to prepare a separator for an electrochemical device.

Comparative Example 3

The same polyolefin film as used in Example 1 was heat set at 130 DEG C, and then the same porous coating layer-forming slurry as used in Example 1 was coated on one side to a thickness of 3.5 mu m, And then a separator for an electrochemical device was fabricated.

Comparative Example 4

After extrusion at 210 占 폚 as in Example 1, annealing was performed at 110 占 폚. The slurry for forming the porous coating layer as used in Example 1 was coated on the annealed film to a thickness of 3.5 탆 and stretched at a draw ratio of 7 at 115 캜. Thereafter, extraction was carried out in the same manner as in Example 1, and the resultant was again opened at 132.5 ° C at a rate of 5 M / min to prepare a separator for electrochemical devices. The thus-prepared separator was inadequate for use as a separator because the coating layer was peeled off while being stretched after coating.

Evaluation example

The aeration time, tensile strength, heat shrinkage and moisture content of each of the separators for electrochemical devices according to Example 1 and Comparative Example 1 were measured, and the results are shown in Table 1 below.

(1) Measurement of ventilation time

The time (sec) required for 100 ml of air to pass through the separator was measured at a constant pressure (0.05 MPa) using an air flow meter (Maker: Asahi Seiko, Model: EG01-55-1MR). A total of 3 points were measured for each point of left / middle / right of the sample, and the average was recorded.

(2) Measurement of tensile strength

Using a tensile strength tester (manufacturer: Instron: model name: 3345 UTM)

At the speed, the membrane sample (length: 12 cm, width 1.5 cm) was pulled at both ends of the specimen, and the strength measured as the maximum value of the strength to withstand the specimen was measured three times and the average was recorded.

(3) Heat shrinkage measurement

The membrane sample (size: 50 mm x 50 mm) was stored at 120 ° C and 60 min using a convection oven and the length of the part where the shrinkage was most severely occurred at room temperature was measured using a steel ruler. The heat shrinkage ratio Respectively. A total of 3 points were measured for each 1 point of left / middle / right of the sample, and the average was recorded.

Heat shrinkage percentage (%) = [1- (length of shrinkage most severe portion) / (initial length)] X 100

(4) Measurement of moisture content

After a blank test at an oven temperature of 120 ° C using a Karl Fisher (Mettler toledo) equipment, nitrogen gas was introduced into a vial containing about 0.5 to 0.6 g of a separation membrane, and the extraction time was set to 5 minutes. Were measured. A total of 3 points were measured for each of the left, middle, and right sides of each membrane sample, and the average was recorded.

Condition Comparative Example 1
(Conventional process: heat fixation → coating) Example 1
(Improvement process: coating → heat fixation) division fabric Composite membrane Composite membrane Oven Heat-setting oven Coating Drying Oven Heat-setting oven Oven length M 5 5 One Oven temperature ℃ 130 70 132.5 Composite membrane
thickness ㎛ 11.0 14.5 14.5 Ventilation time Sec / 100ml 170 240 200 The tensile strength MD Kg / cm ² 1800 1800 2300 TD 1700 1700 2150 Heat shrinkage
(120 ° C / 1 hr) MD Kg / cm ² 10 7 6 TD 10 5 3 Moisture content
(120 DEG C / 5 min) ppm - 825 770

When comparing the results shown in Table 1 with those of Example 1 and Comparative Example 1 in which the heat fixing process was performed differently and the same raw materials were used, the plasticizer was extracted from the polyolefin film, and then the slurry containing the inorganic particles was coated. Shows a tensile strength and a heat shrinkage ratio that are superior to those of Comparative Example 1.

Improvement in performance such as improvement of tensile strength and reduction of heat shrinkage can be achieved by performing slurry coating on the raw material of the slurry and then thermally fixing the slurry, (Comparison 1), it can be concluded that the result is obtained by performing heat fixation at a higher temperature.

In addition, taking such a high heat setting temperature has the advantage of space utilization because the length of the heat-setting oven can be further reduced, which not only makes it possible to reduce the production cost, It has an advantage that it can be applied to a moisture sensitive battery having a low moisture content.

Next, the aeration time, tensile strength, heat shrinkage, and moisture content of each of the separators for electrochemical devices according to Example 2 and Comparative Example 2 were measured, and the results are shown in Table 2 below.

Condition Comparative Example 2
(Conventional process: heat fixation → coating) Example 2
(Improvement process: coating → heat fixation) division fabric Composite membrane Composite membrane Oven Heat-setting oven Coating Drying Oven Heat-setting oven Oven length M 5 5 One Oven temperature ℃ 130 70 133 Composite membrane thickness ㎛ 12.0 20.0 20.0 Ventilation time Sec / 100ml 230 340 270 The tensile strength MD Kg / cm ² 1800 1850 2300 TD 1400 1450 1800 Heat shrinkage
(120 ° C / 1 hr) MD Kg / cm2 7 5 4 TD 5 3 2 Moisture content
(120 DEG C / 5 min) ppm - 910 898

The results are shown in Table 2. Referring to the results shown in Table 2, the separation membrane according to Example 2 in which the heat fixation process was performed after the coating was performed after the heat fixation process in Comparative Example 2, In comparison, it can be seen that it exhibits better tensile strength, heat shrinkage and moisture content characteristics.

Next, the aeration time, tensile strength, heat shrinkage and moisture content of each of the separators for electrochemical devices according to Example 1 and Comparative Example 3 were measured, and the results are shown in Table 3 below.

Condition Comparative Example 3
(Conventional process: heat fixation → coating) Example 1
(Improvement process: coating → heat fixation) division fabric Composite membrane Composite membrane Oven Heat-setting oven Coating Drying Oven Heat-setting oven Oven length M 5 5 One Oven temperature ℃ 130 132.5 132.5 Composite membrane thickness ㎛ 11.0 14.5 14.5 Ventilation time Sec / 100ml 170 255 200 The tensile strength MD Kg / cm ² 1800 1800 2300 TD 1700 1750 2150 Heat shrinkage
(120 ° C / 1 hr) MD Kg / cm ² 10 7 6 TD 10 4 3 Moisture content
(120 DEG C / 5 min) ppm - 735 770

Referring to the results shown in Table 3, in Comparative Example 3, a composite membrane was prepared under the same coating conditions as in Example 1 on one side of a conventional 130 ° C heat-set fabric. In this case, since fibrillation was carried out before the slurry coating (annealing) on the fabric, the fibril binding has already been completed. When the fibril intergranulation is completed, the mechanical strength and the thermal characteristics are not greatly improved because reattachment between coarse fibrils is not easy even if the heat fixation is performed again at a temperature below Tm. Further, since the binding force between the porous coating layer and the porous polyolefin film is not formed, it is difficult to exhibit the same excellent physical properties as in Example 1.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

Claims (21)

Extruding a resin composition containing a polyolefin and a plasticizer;
Stretching the extruded resin composition to obtain a polyolefin film;
Extracting the plasticizer from the obtained polyolefin film to obtain a porous polyolefin film;
Coating at least one surface of the porous polyolefin film with a slurry for forming a porous coating layer; And
Wherein the slurry-coated porous polyolefin film is heat-set to obtain a composite membrane having a porous coating layer formed thereon. The method according to claim 1,
Wherein the extruded resin composition is subjected to uniaxial stretching at least once in the MD direction or TD direction or by biaxial stretching at least once in the MD and TD directions. The method according to claim 1,
Wherein the open and the defined temperature are Tm - 1 DEG C or less, wherein Tm is the melting point of the polyolefin. The method according to claim 1,
Wherein the open and the defined temperature ranges from 131 ° C to 134 ° C. The method according to claim 1,
Wherein the heat setting is performed using a heat source oriented in a direction perpendicular to the surface of the slurry coated on the porous polyolefin film. The method according to claim 1,
Wherein the polyolefin is selected from the group consisting of polyethylene; Polypropylene; Polybutylene; A process for producing a separator for electrochemical devices, which comprises: a polyphenylene: polyhexene: polyolefin: at least one copolymer selected from the group consisting of ethylene, propylene, butene, pentene, 4-methylpentene, hexene and octene; Way. The method according to claim 1,
Examples of the plasticizer include paraffin oil, mineral oil, wax, soybean oil, phthalic acid esters, aromatic ethers, fatty acids having 10 to 20 carbon atoms; Fatty acid alcohols having 10 to 20 carbon atoms; And at least one selected from the group consisting of aliphatic acid esters and fatty acid esters. The method according to claim 1,
Wherein the porous polyolefin film has a thickness of 5 to 50 μm and a pore size and a porosity of 0.01 to 50 μm and 10 to 95%, respectively. The method according to claim 1,
Wherein the slurry for forming a porous coating layer comprises at least one of inorganic particles and organic particles, a binder polymer, and a solvent. 10. The method of claim 9,
The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, Polybutylene terephthalate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyethylene) oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylpolyvinylalcohol, No ethylcellulose But are not limited to, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, Or a mixture thereof. &Lt; / RTI &gt; 10. The method of claim 9,
Wherein the inorganic particles are inorganic particles having a dielectric constant of 5 or more and lithium ion transferring ability or a mixture thereof. 12. The method of claim 11,
Wherein the inorganic particles having a dielectric constant of 5 or more are BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) ₃ O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO _2, SiC Or a mixture thereof. &Lt; / RTI &gt; 12. The method of claim 11,
Wherein the inorganic particles having lithium ion transferring ability are lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y series glass (0 < 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , x <4, 0 <y < 1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 based glass ( _{Li x Si y S z, 0} <x <3, 0 <y <2, 0 <z <4), P 2 S 5 based _{glass (Li x P y S z} , 0 <x <3, 0 <y < 3, 0 < z < 7) or a mixture thereof. 10. The method of claim 9,
Wherein the organic particles are selected from the group consisting of polystyrene, polyethylene, melamine resin, phenol resin, cellulose, cellulose modified product, polypropylene, polyester, polyphenylene sulfide, polyaramid, polyamideimide, polyimide, butyl acrylate, Wherein the copolymer is a copolymer of ethylene and propylene or a mixture thereof. The method according to claim 1,
Wherein the inorganic particles and the organic particles have an average particle diameter of 0.001 to 10 mu m, respectively. The method according to claim 1,
Further comprising the step of winding and slitting the composite separator. &Lt; Desc / Clms Page number 19 &gt; The method according to claim 1,
Wherein the step of coating the slurry for forming a porous coating layer does not include a step of heat setting and a step of winding and slitting. 17. The method of claim 16,
The method of claim 1, further comprising packaging the composite separator after completion of the winding and slitting. 18. A separator for an electrochemical device, which is produced by the method according to any one of claims 1 to 18. An electrochemical device comprising a cathode, an anode, and a separator interposed between the cathode and the anode,
The electrochemical device according to claim 19, wherein the separator is a separator for an electrochemical device. 21. The method of claim 20,
Wherein the electrochemical device is a lithium secondary battery.

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